The preferred method is to strip all the old filler off and remove all rust that was under the filler. I would then apply an epoxy primer, followed by all required body work, followed by a high build primer/surfacer.

Vince

 

epoxy

got agallon of dp800 epoxy was told mix 8parts primer 4 parts reducer 1 part activator sprayed on sandblasted fender had surface rust in 2days is this the right ratio or what any help is app

 

Not to steal the thread, but I also was wondering, since I am taking my car down to bare metal, and was planning on using SPI Epoxy primer then SPI 2k...would that be fine for bare metal...because now it seems as though self etching would be needed...

 

Not to steal the thread, but I also was wondering, since I am taking my car down to bare metal, and was planning on using SPI Epoxy primer then SPI 2k...would that be fine for bare metal...because now it seems as though self etching would be needed...

That is a solid procedure, and will produce a superb base for final paint.

Vince

 

I am working on a 49 Chev car, and as I strip the paint, I am finding old bondo and some areas where there is surface rust under the bondo and old paint. Some of the paint has also been chipped as well having surface rust. I was planning on using PPG MP 170 Epoxy, but after doing some reading on the net, it sounds like a self etching primer would be the course. The article stated that on older restorations, it is better use a self etching primer for metal with surface rust. The article also said that self etch primer was better for corrosion resistance. HUh.... I thought epoxy was the way to go, ofcourse I have not painted since the old DP primer was the thing to use, or is epoxy still the way to go.

If I go with self etch, here is what I was thinking to do. First I have some large weld seams in this body, and I know there may be a few small pinholes in the weld areas. Had a hell of a time with the 110 mig in some areas. On the weld areas, I am planning on using POR15 and seam sealer on the back of the welds, MP epoxy on the outside, filler on top of MP170. I was then thinking maybe spray the body with self etch primer and then 2K, block and paint. My thinking with the MP under the filler was that it would help seal the weld areas from moisture and I already have about a quart from another project. I was then thinking that th etch on top would be the way to go since I thought I read etch primer and filler do not get along well. Can I go ahead and spray etch primer and do filler over that or what is the best way to go in this case?

I would start with clean metal then prime with epoxy let cure and do your repair filler work and prime with a 2k primer surfacer like K36

 

there is no reason to use etch primer . except for someone to sell it to you.

 

There is no place in modern autobody work for self etching primer.
Modern epoxy has all the bases covered.

 

Save your money ,self etching primer will cause problems...
I've used just about every kind of primer there is and found that SPI works the best over clean, bare metal...and the cost is right...
Getting rid of rust is a whole other story, but once its gone prime right away..One panel at a time.You can do your body work over the primer and it wont rust under the bondo...

 

what kind of problems are we talking here?

 

what kind of problems are we talking here?

first off it is not water proof and I had a problem years ago when I used it to spot prime in the booth and had a white car that the primer stained the old paint it didnt show up until the car was cleared then had a orange spot where I sprayed the primer

 

And bondo wont stick to it....Epoxy sticks pretty well to it but if you have to epoxy it why use etch to begin with?
I used Vari prime for years,it'll wash off with lacquer thinner.we used it for better adhesion with lacquer primer to bare metal...epoxy replaced it,it's much better....

 

Epoxy vs Etching Primers Over Metals

I have tired both methods of primers Epoxy and Etching primer. I did a 57 chevy bare metal shot epoxy primer over it, did my body work. Filler etc...

Before you prime it make sure the metal is flat as possible so you won't go crazy banging high spots down and refilling.

Prime the metal with epoxy primer, do your bodywork, sand filler using 320-360 grit before priming with 2k primer.

Check bodywork, I would block sand it, 2k high build primer the rest of the car, even non metal areas, over filler, over everything. block sand, seal, base and clear.

Although you can paint base directly over your 2k primer. I've had beautiful finishes painting right over 2k primer.

Hope that helps!!

for more tips check out this ebook. Its free.
http://www.learnautopainting.com/pdf/new-paint-manual.pdf

Cheers!

T :welcome:

I am working on a 49 Chev car, and as I strip the paint, I am finding old bondo and some areas where there is surface rust under the bondo and old paint. Some of the paint has also been chipped as well having surface rust. I was planning on using PPG MP 170 Epoxy, but after doing some reading on the net, it sounds like a self etching primer would be the course. The article stated that on older restorations, it is better use a self etching primer for metal with surface rust. The article also said that self etch primer was better for corrosion resistance. HUh.... I thought epoxy was the way to go, ofcourse I have not painted since the old DP primer was the thing to use, or is epoxy still the way to go.

If I go with self etch, here is what I was thinking to do. First I have some large weld seams in this body, and I know there may be a few small pinholes in the weld areas. Had a hell of a time with the 110 mig in some areas. On the weld areas, I am planning on using POR15 and seam sealer on the back of the welds, MP epoxy on the outside, filler on top of MP170. I was then thinking maybe spray the body with self etch primer and then 2K, block and paint. My thinking with the MP under the filler was that it would help seal the weld areas from moisture and I already have about a quart from another project. I was then thinking that th etch on top would be the way to go since I thought I read etch primer and filler do not get along well. Can I go ahead and spray etch primer and do filler over that or what is the best way to go in this case?

 

there is no reason to use etch primer . except for someone to sell it to you.

I won't even carry it in the store shine.. I see no need for it..
Some people get upset but I feel safer that way.

 

Epoxy is the way to go.. :thumbup: